Device for transporting heat from a lower to a higher temperature level

ABSTRACT

A device for transporting heat between two temperature levels which are situated below 1*K, provided with a mixing chamber having an inlet duct for the supply of a medium flow consisting mainly of 3He. The mixing chamber is connected, via a connection duct which is in heat-exchange with the inlet duct, to an evaporation reservoir. The mixing chamber, the connection duct and the evaporation reservoir contain a mixture of 4He and 3He during operation. The evaporation reservoir is provided with an outlet for mainly 3He in the vapour phase, and the device furthermore comprises at least one superleak, one side of which opens into and near the bottom of the evaporation reservoir. Its other side communicates with a space provided with a heating device, the said space communicating, via a narrow duct and a cooler, with a duct in which a number of superleaks are arranged. Between the super-leaks heat-exchanging chambers are arranged which exchange heat with the connection duct and the inlet duct. The other end of this inlet duct opens into the upper part of a second mixing chamber. The first and the second mixing chamber are interconnected by a further connection duct which opens into the lower part of the second and into the upper part of the first mixing chamber.

United States Patent DEVICE FOR TRANSPORTING HEAT FROM A LOWER TO A HIGHER TEMPERATURE LEVEL [75] Inventors: Frans Adrianus Staas; Adrianus Petrus Severijns, both of Eindhoven, Netherlands [73] Assignee: U.S. Philips Corporation, New

York, N.Y.

[22] Filed: Mar. 14, 1973 [21] Appl. No.: 340,954

[30] Foreign Application Priority Data Mar. 18, 1972 Netherlands [52] US. Cl. 62/467, 62/514 [51] Int. Cl. F25b [58] Field of Search 62/467, 514

[56] References Cited UNITED STATES PATENTS 3,195,322 7/1965 London 62/467 3,376,712 4/1968 London 62/467 3,447,333 6/1969 Goodstein 62/514 3,472,038 10/1969 Staas 62/467 3,581,512 6/1971 Stass 62/514 3,589,138 6/1971 Severijns 62/514 3,678,704 7/1972 Staas 62/514 3,713,305 1/1973 Stass 62/514 Sept. 17, 1974 Primary Examiner-William J. Wye Attorney, Agent, or FirmFrank R. Trifari [5 7] ABSTRACT A device for transporting heat between two temperature levels which are situated below 1K, provided with a mixing chamber having an inlet duct for the supply of a medium flow consisting mainly of He. The mixing chamber is connected, via a connection duct which is in heat-exchange with the inlet duct, to an evaporation reservoir. The mixing chamber, the connection duct and the evaporation reservoir contain a mixture of *He and He during operation. The evaporation reservoir is provided with an outlet for mainly He in the vapour phase, and the device furthermore comprises at least one superleak, one side of which opens into and near the bottom of the evaporation reservoir. Its other side communicates with a space provided with a heating device, the said space communicating, via a narrow duct and a cooler, with a duct in which a number of superleaks are arranged. Between the super-leaks heat-exchanging chambers are arranged which exchange heat with the connection duct and the inlet duct. The other end of this inlet duct opens into the upper part of a second mixing chamber. The first and the second mixing chamber are interconnected by a further connection duct which opens into the lower part of the second and into the upper part of the first mixing chamber.

2 Claims, 1 Drawing Figure DEVICE FOR TRANSPORTING HEAT FROM A LOWER TO A HIGHER TEMPERATURE LEVEL BACKGROUND OF THE INVENTION The invention relates to a device for transporting heat from a lower to a higher temperature level, both levels being situated below lK. The device comprises a mixing chamber which is provided with an inlet duct for the supply of a medium flow consisting mainly of He. The mixing chamber communicates, via a connection duct which is in heat exchange with the inlet duct, with an evaporation reservoir, the mixing chamber, the connection duct and the evaporation reservoir containing a mixture of He and He. During operation, the evaporation reservoir is provided with an outlet for mainly He in the vapor phase. The device furthermore comprises at least one superleak, one side of which opens into and near the bottom of the evaporation reservoir.

A device of the kind set forth is known from U.S. Pat. No. 3,195,322 (FIG. 10). In this known device, the mixing chamber which is at 0.1 K, the connection duct and the evaporation space which is at 0.65K contain a mixture of He and He. The evaporation space is kept at this low temperature by the withdrawal of vapor which consists mainly of He as a result of its higher volatility Via the inlet duct, exchanging heat with the connection duct, a medium flow containing mainly He is applied to the mixing chamber. Below O.9K, phase separation takes place in liquid He-He mixtures, i.e. into a He-rich phase and a He-poor phase. This phase separation occurs in the mixing chamber. The transition from the supplied He-rich phase to the I-Ie-poor phase involves dilution and the mixing heat required for this purpose produces a cooling effect. Subsequently, the He in the superfluid He present in the connection duct will expand, thus producing a large quantity of cold which, however, is required substantially completely for the cooling of the He-flow in the inlet duct. The described cooling effect is thus obtained by the circulation of the He. So as to improve the cooling effect, the known device proposes to connect the evaporation space via a super-leak to a He-bath having a temperature of approximately 1.3 K. He is applied from the *He-bath to a space which is connected, via a second super-leak, to the connection duct at a location be tween the mixing chamber and the evaporation reservoir. This construction serves to cause a turbulent *He flow in the connection duct, which would result in an additional cooling effect in the mixing chamber. To achieve such a turbulent flow of He in the outlet duct, however, it is necessary that the required driving force is generated somewhere in the He-circuit, formed by the evaporation reservoir, the first superleak, the second superleak, the mixing chamber and the connection duct. A drawback of the known device is that the required driving force is not obtained or at least not to an extent which is sufficient to ensure proper operation.

A device of the kind to which the present invention relates is also described in U.S. Pat. No. 3,376,712 in which, so as to improve the cooling effect obtained by the phase transition from the He-rich phase to the Hepoor phase in the mixing chamber, the evaporation reservoir is connected, via a duct incorporating a superleak, to a part of the connection duct between mixing chamber and evaporation reservoir, it being possible to isolate this part from the mixing chamber of the evaporation reservoir, or from both, by means of valves. Correct control of the valves produces a kind of steam engine cycle, in which a mixture containing He expands further into substantially pure He which is supplied from the evaporation reservoir via the super-leak. Because the driving force for the supply of the He is merely the osmotic pressure difference across the superleak, this effect will only be limited. A further drawback of the device is its complexity and the fact that the valves operate at a very low temperature (wear and heat leakage).

SUMMARY OF THE NEW INVENTION The invention has for its object to provide a device in which said drawback is eliminated; to this end it is characterized in that the side of the superleak which is remote from the evaporation reservoir communicates with a space provided with a heating device for the supply of heat. This space communicates, via a narrow duct in which the helium exceeds its critical velocity and a cooler, with a duct in which a number of superleaks are arranged. Heat exchanging chambers are arranged between these superleaks, said heat-exchanging chambers forming part of heat exchangers which also comprise heat-exchanging chambers which are incorporated in the connection duct and the inlet duct. The other end of the duct opens into the upper part of a second mixing chamber which is arranged at a level higher than that of the first timing chamber; the first and second mixing chamber are interconnected by a further connection duct which opens into the lower part of the second mixing chamber and into the upper part of the first mixing chamber, the duct being in heat-exchange, prior to opening into the second mixing chamber, with the first mixing chamber and the further connection duct.

In the device according to the invention, the supply of heat to said space will cause a fountain pumping action across the first superleak, the superfluid helium then flowing from the evaporation reservoir to said space. The helium flows through the narrow duct in which it exceeds its critical velocity to the cooler and the inlet of the second superleak. The series connection of first superleak, narrow duct and cooler thus creates a driving force on the *He which is sufficient to make the He circulate through the ducts comprising the super-leaks, the first and the second mixing chamber, and the connection ducts and then back to the evaporation reservoir again. A striking aspect is that by means of this device, whose operation will yet be described in detail, a temperature of approximately 0.6 mK can be achieved in the second mixing chamber.

The invention will be described in detail with reference to the drawing which diagrammatically shows an embodiment of a device for transporting heat from a lower to a higher temperature level.

DESCRIPTION OFTHE PREFERRED EMBODIMENT The reference numeral 1 denotes a first mixing chamber. An inlet duct 2 for He communicates with this mixing chamber 1. The mixing chamber 1 is also connected, by a connection duct 3, to an evaporation reservoir 4 which is provided with an outlet 5 for He in the vapor phase. The outlet 5 can be connected, for example, to a gas pump not shown. The inlet duct 2 and the connection duct 3 are in heat-exchanging contact with each other via heat exchangers 6, 7, 8 and 9. The mixing chamber 1, the connection duct 3 and the evaporation reservoir 4 are filled with a He-l-le mixture. The evaporation reservoir 4 is connected to a superleak 10, the other side of which is connected to a space 11 in which a heating coil 12 is arranged. The space 11 is connected, via a narrow duct 13 and a cooler 14, to one side of a duct 15 which comprises a number of superleaks and heat-exchanging chambers which are arranged therebetween and which form part of the heat exchangers 6, 7, 8 and 9. Behind the last exchanger 6, the duct 15 is also in heat-exchange with the first mixing chamber 1 at the area 16, and subsequently in heat exchanger 17 with the connection duct 18 between the first mixing chamber 1 and a second mixing chamber 19 in which the duct 15 opens at the top. In given circumstances, the heat exchanger 17 may be omitted.

The operation of this device is as follows. Mixing chamber 1, connection duct 3 and evaporation reservoir 4 are filled with a He- He mixture. Via outlet 5, mainly He which is more volatile than He is discharged. Via inlet duct 2, mainly He is supplied to mixing chamber 1 in which the applied He-rich phase changes over into the He-poor phase, which is accompanied by developments of cold, it being possible to utilize this cold for the cooling of some object. The He subsequently flows through the connection duct 3 to the evaporation reservoir 4 again.

in addition, because in space 11 a temperature is adjusted, by means of the heating coil 12, which is slightly higher than that in reservoir 4, He is transported from reservoir 4 through superleak 10 to space 11 as a result of the fountain pumping action. An additional advantage thereof is that this withdrawal of He is accompanied by heat development in reservoir 4, so that the evaporation of He can be effected without additional heating. This He flows from the space 11, via duct 13 and cooler 14, to the inlet of superleak 15. As a result of the series connection of superleak 10, space 1 1, duct 13 and cooler 14, such a driving force is exerted on this He that a high pressure is obtained on the inlet of duct 15. This high pressure ensures that superfiuid He flows against the temperatire gradient through the duct 15 to the other side of this duct. During this flowing, heat is exchanged with the connection duct where further expansion of He to He produces additional cold, so that the He is properly cooled. Further cooling takes place at the area 16 where the He exchanges heat with the very cold mixture in the mixing chamber 1.

The second mixing chamber 19 communicates, via connection duct 18, with mixing chamber 1, a heat exchanger 17 ensuring heat exchange between the He in duct 15 and the mixture in the connection duct 18.

The He ultimately enters the mixing chamber 19 in which the He-rich phase (already present in mixing chamber 19) is diluted by the supplied He, thus producing cold. Due to its weight, the mixture formed drops through duct 18 to mixing chamber 1 and from there it circulates via duct 3 to evaporator 4. in the device according to the invention, consequently, cold is produced at two levels, i.e. in the mixing chamber 1 at a temperature of approximately 0.05K and in mixing chamber 19 at a temperature of approximately 0.6 ml(. Notably this latter temperature cannot be achieved by means of the known device.

What is claimed is:

1. A device for transporting heat from a lower to a higher temperature level, both temperature levels being situated below 1K, the said device comprising a mixing chamber which is provided with an inlet duct for the supply of a medium flow which consists mainly of He, the said mixing chamber communicating, via a connection duch which is in heat exchange with the inlet duct, with an evaporation reservoir the mixing chamber, the connection duct and the evaporation reservoir containing a mixture of He and He during operation, the evaporation reservoir being provided with an outlet for mainly *He in the vapour phase, the device furthermore comprising at least one superleak, one side of which opens into and near the bottom of the evaporation reservoir, characterized in that the side of the said superleak which is remote from the evaporation reservoir communicates with a space provided with a heating device for the supply of heat, the said space communicating, via a narrow duct in which the helium exceeds its critical velocity and a cooler, with a duct in which a number of superleaks are arranged, heatexchanging chambers being arranged between these superleaks, the said heat-exchanging chambers forming part of heat exchangers which also comprise heat exchanging chambers which are incorporated in the connection duct and the inlet duct, the other end of the said duct opening into the upper part of a second mixing chamber which is arranged at a level higher than that of the first mixing chamber, the first and the second mixing chamber being interconnected by a further connection ducg which opens in the lower part of the second mixing chamber and into the upper part of the first mixing chamber, the duct being in heat-exchange, prior to opening into the second mixing chamber, with the first mixing chamber and possibly with the further connection duct.

2. A device for transporting heat from a lower to a higher temperature level, both temperature levels being situated below lK, said device comprising a mixing chamber which is provided with a first inlet duct for the supply of a flow of medium comprising mainly He, and a second connection duct in heat exchange with said first duct, the mixing chamber communicating via said second duct with said evaporation reservoir, the mixing chamber, the connect duct and the evaporation reservoir containing a mixture of He and He during operation, the evaporation reservoir being provided with an outlet mainly for He in the vapor phase, the device furthermore comprising at least one superleak having one side which opens into and near the bottom of the evaporation reservoir and an opposite side which is remote from the evaporation reservoir, the device further comprising a heating space, a heating device therein, a third duct comprising a plurality of superleaks arranged alternately in series with heatexchanging chambers and defining opposite ends thereof, a cooler, a fourth narrow duct connecting said cooler and said space, a second mixing chamber at an altitude higher than that of the first mixing chamber, a further connection duct interconnecting the lower part of the second mixing chamber with the upper part of the first mixing chamber, said heating space communicating with said opposite side of the superleak and also communicating via said narrow duct in which the helium exceeds its critical velocity and said cooler with one end of said third duct, the other end of the said third duct opening into the upper part of said second mixing chamber, the third duct being in heat-exchange, prior to opening into the second mixing chamber, with the first mixing chamber. 

1. A device for transporting heat from a lower to a higher temperature level, both temperature levels being situated below 1*K, the said device comprising a mixing chamber which is provided with an inlet duct for the supply of a medium flow which consists mainly of 3He, the said mixing chamber communicating, via a connection duch which is in heat exchange with the inlet duct, with an evaporation reservoir the mixing chamber, the connection duct and the evaporation reservoir containing a mixture of 4He and 3He during operation, the evaporation reservoir being provided with an outlet for mainly 3He in the vapour phase, the device furthermore comprising at least one superleak, one side of which opens into and near the bottom of the evaporation reservoir, characterized in that the side of the said superleak which is remote from the evaporation reservoir communicates with a space provided with a heating device for the supply of heat, the said space communicating, via a narrow duct in which the helium exceeds its critical velocity and a cooler, with a duct in which a number of superleaks are arranged, heatexchanging chambers being arranged between these superleaks, the said heat-exchanging chambers forming part of heat exchangers which also comprise heat-exchanging chambers which are incorporated in the connection duct and the inlet duct, the other end of the said duct opening into the upper part of a second mixing chamber which is arranged at a level higher than that of the first mixing chamber, the first and the second mixing chamber being interconnected by a further connection ducg which opens in the lower part of the second mixing chamber and into the upper part of the first mixing chamber, the duct being in heatexchange, prior to opening into the second mixing chamber, with the first mixing chamber and possibly with the further connection duct.
 2. A device for transporting heat from a lower to a higher temperature level, both temperature levels being situated below 1*K, said device comprising a mixing chamber which is provided with a first inlet duct for the supply of a flow of medium comprising mainly 3He, and a second connection duct in heat exchange with said first duct, the mixing chamber communicating via said second duct with said evaporation reservoir, the mixing chamber, the connect duct and the evaporation reservoir containing a mixture of 4He and 3He during operation, the evaporation reservoir being provided with an outlet mainly for 3He in the vapor phase, the device furthermore comprising at least one superleak having one side which opens into and near the bottom of the evaporation reservoir and an opposite side which is remote from the evaporation reservoir, the device further comprising a heating space, a heating device therein, a third duct comprising a plurality of superleaks arranged alternately in series with heat-exchanging chambers and defining opposite ends thereof, a cooler, a fourth narrow duct connecting said cooler and said space, a second mixing chamber at an altitude higher than that of the first mixing chamber, a furtheR connection duct interconnecting the lower part of the second mixing chamber with the upper part of the first mixing chamber, said heating space communicating with said opposite side of the superleak and also communicating via said narrow duct in which the helium exceeds its critical velocity and said cooler with one end of said third duct, the other end of the said third duct opening into the upper part of said second mixing chamber, the third duct being in heat-exchange, prior to opening into the second mixing chamber, with the first mixing chamber. 